The gallbladder stores bile which is a very concentrated solution of bile salts, bilirubin and cholesterol. These chemicals are produced by the liver in large amounts and are necessary for the digestion of fat.
Crystals of these compounds can occur in the gallbladder spontaneously when their concentration becomes too high. These crystals may grow to become stones of any size. We have seen stones as large as billiard balls.
Not everyone that has gallstones has problems. The stones may lie silently in the gallbladder and never cause a problem. We do not know why some stones cause problems and others do not. But when they do cause problems we know those patients need their gallbladder removed.